Field of the Invention
The present invention relates to a communication apparatus, which can be mounted on an image pickup apparatus such as a digital camera, and a communication control method therefor.
Description of the Related Art
In general, a remote controller is used to remotely instruct an image pickup apparatus such as a digital camera or a cellular phone to execute a shooting operation.
A camera system which remotely instructs an image pickup apparatus as mentioned above to execute a shooting operation in Japanese Laid-Open Patent Publication (Kokai) No. H05-61109 uses an external strobe, which is not mounted on the image pickup apparatus, as a remote controller to remotely instruct the image pickup apparatus to execute a shooting operation. In particular, according to Japanese Laid-Open Patent Publication (Kokai) No. H05-61109, when a photometric means of the image pickup apparatus detects stroboscopic light from the external strobe which is not mounted on the image pickup apparatus, the image pickup apparatus executes a shooting operation.
The above described method (first method) that uses a remote controller to remotely instruct an image pickup apparatus to execute a shooting operation requires the image pickup apparatus to have a receiver that receives signals from the remote controller. A receiver that can be removably mounted on an image pickup apparatus should be mounted on an image pickup apparatus having no receiver, but in this case, the image pickup apparatus needs to have a controller for executing a shooting operation based on a result of receipt by the receiver.
On the other hand, as a method of remotely instructing an image pickup apparatus to execute a shooting operation, there is known a method (second method) that uses a cable (hereafter referred to as a release cable) for transmitting a signal for instructing an image pickup apparatus to execute a shooting operation (hereafter referred to as a release signal). According to this method, as long as the release cable is connectable to an image pickup apparatus, the image pickup apparatus can be remotely instructed to execute a shooting operation even when the image pickup apparatus has no receiver and no control section like the first method.
However, for conventional image pickup apparatuses, no consideration is given to how to use a plurality of methods to remotely instruct an image pickup apparatus to execute a shooting operation such as the first and second methods described above. For example, when the second method is used, an instruction to execute a shooting operation is given to an image pickup apparatus by an interrupt of a release signal, and hence the time required to start the shooting operation after a user gives the instruction is shorter as compared to the first method. On the other hand, when an instruction to execute a shooting operation is given to an image pickup apparatus by an interrupt of a release signal in a state in which a shooting preparation process such as an AF (auto-focus) process has not been completed, it can be considered that the shooting operation will not be executed because a higher priority is given to the AF process.